The invention relates to edible fat-containing products comprising indigestible polyol fatty acid polyesters. In particular, although not exclusively, the invention relates to such products of the emulsion type, such as margarines and low-fat spreads. The invention further relates to processes for the preparation of such products.
Polyol fatty acid polyesters, and in particular, the sugar fatty acid polyesters, such as e.g. the sucrose fatty acid polyesters, are known as suitable low-calorie fat-replacers in edible products. Substantially indigestible for human beings they have physical and organoleptic properties very similar to triglyceride oils and fats conventionally used in edible products. Polyol fatty acid polyesters are also reported to have use as pharmaceutical agents e.g. in view of their ability to take up fat-soluble substances, such as in particular cholesterol, in the gastro-intestinal tract, and subsequently remove those substances from the human body. Accordingly, it is attractive to replace at least part of the fat in edible fat-containing products by polyol fatty acid polyesters.
It is further reported that in food products the use of polyol fatty acid polyesters which are liquid at body temperature, may give rise to the so-called problem of anal leakage. Accordingly, it is particularly attractive to replace the more solid part (hardstock) of the fat by counter-part polyol fatty acid polyesters.
Edible fat-containing products comprising indigestible polyol fatty acid polyesters are known in the art, and described in eg U.S. Pat. Nos. 3,600,186, 4,005,195, 4,005,196, 4,034,083 and EP Pat. Publ. Nos. 0 233 856, 0 236 288, and 0 235 836.
In this specification, unless otherwise indicated, the term 'fat' refers to edible fatty substances in a general sense, including natural or synthesized fats and oils consisting essentially of triglycerides such as, for example, soybean oil, sunflower oil, palm oil, coconut oil, fish oil, lard and tallow, which may have been partially or completely hydrogenated or modified otherwise, as well as non-toxic fatty materials having properties similar to triglycerides, which materials may be indigestible, such as for example waxes, e.g. jojoba oil and hydrogenated jojoba oil, and polyol fatty acid polyesters referred to hereinafter in more detail. The terms fat and oil are used interchangeably.
In this specification the term 'polyol' is intended to refer to any aliphatic or aromatic compound which comprises at least four free hydroxyl groups. Such polyols in particular include the group of sugar polyols, which comprises the sugars, i.e. the mono-, di-and polysaccharides, the corresponding sugar alcohols and the derivatives thereof having at least four free hydroxyl groups. Examples of sugar polyols include glucose, mannose, galactose, xylose, fructose, sorbose, tagatose, ribulose, xylulose, maltose, lactose, cellobiose, raffinose, sucrose, erythritol, mannitol, lactitol, sorbitol, xylitol and alpha-methylglucoside. A generally used sugar polyol is sucrose.
In this specification the term 'polyol fatty acid polyester' is intended to refer to any such polyesters or mixtures thereof of which, on an average, more than 70 % of the polyol hydroxyl groups have been esterified with fatty acids.
In this specification by 'indigestible' is meant that at least about 70 % by weight of the material concerned is not digested by the human body.
In this specification by 'hardstock' is meant that part of the fat composition characterized by a slip melting point of above 36.degree. C. 'Slip melting point' is defined as the temperature at which the amount of solid phase in the melting fat has become so low that an air bubble is forced upwards in an open capillary filled with the fat.
Fat-containing products and in particular, emulsion-type products such as margarines and low-fat spreads, have to comply with requirements such as oral response, thermal stability, cycle stability, spreadability, melting behaviour and the like. Often they have to comply with such requirements simultaneously.
In particular, for margarines and low-fat spreads which contain relatively large amounts of polyunsaturated components, or require increased softness at lower (refrigerator) temperatures, it can be difficult to simultaneously comply with the requirements for cycle stability, thermal stability and acceptable taste properties.
Stability against temperature changes (cycle stability) is important in view of temperature changes during transport and storage as well as temperature changes which may frequently occur during household use. Improved storage temperature cycle stability is therefore advantageous, if not essential.
Heat stability, i.e. stability in terms of the absence of phase separation and of oil exudation, determines the ambient temperatures at which the product can be used. It will be clear that heat stability requirements are dependent of the climatic zone involved.
In general the heat stability is governed by the amount of hardstock, i.e. the amount of higher melting fats. A better heat stability, however, in general will result in a deterioration of the oral response, especially after temperature cycling. This is because the oral response largely depends on the melting behaviour of the fat phase.
Although not wishing to be bound by theory, it is believed that the difficult compatibility of heat stability, good oral response and cycling stability stems from the fact that good heat stability (e.g. heat stability at 30.degree. C. for 24 hours) generally requires fat blend compositions containing relatively high amounts of higher melting fat fractions such as in particular fat fractions having melting points above mouth temperature. These higher melting fat fractions are believed to be responsible for the adverse effects on oral response and cycling stability.
Generally, in conventional fat-containing products the higher melting fat fractions crystallize in mixed crystals of non-equilibrium composition, which incorporate considerable amounts of the lower-melting fat fractions. In a well formulated blend the melting point of the mixed crystals is just below mouth temperature. Accordingly, in the mouth such blends will melt entirely, not giving rise to waxiness and, in the case of emulsions, fully releasing the salt and flavour compounds present in the water phase.
However, when conventional fat-containing products are subjected to temperature cycling, the mixed crystals demix, and a separate, purer fraction of the higher melting fats crystallizes. In this process a network of crystals is formed, which, if a dispersed water-phase is present, surrounds and stabilizes the dispersed water droplets in the form of shells. In the mouth the non- or only partially melting network of crystals introduces a waxy taste, and prevents release of salt or flavour compounds from the dispersed water droplets which remain stabilized.
Conventional products displaying good heat stability often combine this property with a rather bad cycling stability and oral response. Vice versa, conventional products having improved cycle stability, due to the presence of a relatively small amount of high melting fats often suffer from a poor heat stability.